Beam change and smoothing in mixed mode WLAN systems

ABSTRACT

A first wireless communication device including a physical layer device configured to generate a data packet having a mixed mode preamble. The mixed mode preamble includes a first portion to be transmitted omnidirectionally via a single stream, and a second portion to be transmitted in a beamformed manner. The mixed mode preamble includes a signal field corresponding to information about the data packet. The signal field includes a first sub-field that indicates a number of streams of the second portion and a second sub-field indicating, based on the first sub-field, whether to perform a beam change between the first portion and the second portion or whether to perform channel smoothing on the second portion. A transceiver is configured to transmit, from the first wireless communication device to a second wireless communication device, the data packet having the mixed mode preamble.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/819,292, filed on May 3, 2013. The entire disclosure of theapplication referenced above is incorporated herein by reference.

FIELD

The present disclosure relates to mixed mode preambles in wireless localarea network communication.

BACKGROUND

Wireless local area networks (WLANs) may include an access point (AP)and one or more client stations. Various operating standards for WLANsinclude, but are not limited to, Institute for Electrical andElectronics Engineers (IEEE) 802.11a, 802.11ac, 802.11af, 802.11ah,802.11b, 802.11g, and 802.11n. Some standards (e.g., 802.11n, 802.11ac,and 802.11ah) implement a mixed mode preamble.

SUMMARY

A first wireless communication device includes a physical layer deviceconfigured to generate a data packet having a mixed mode preamble. Themixed mode preamble includes a first portion to be transmittedomnidirectionally via a single stream, and a second portion to betransmitted in a beamformed manner via a single stream or multiplestreams. The mixed mode preamble includes a signal field correspondingto information about the data packet. The signal field includes a firstsub-field that indicates a number of streams of the second portion ofthe mixed mode preamble and a second sub-field indicating, based on thefirst sub-field, whether to perform a beam change between the firstportion and the second portion of the mixed mode preamble or whether toperform channel smoothing on the second portion of the mixed modepreamble. A transceiver is configured to transmit, from the firstwireless communication device to a second wireless communication device,the data packet having the mixed mode preamble.

A method of operating a first wireless communication device includesgenerating a data packet having a mixed mode preamble. The mixed modepreamble includes a first portion to be transmitted omnidirectionallyvia a single stream, and a second portion to be transmitted in abeamformed manner via a single stream or multiple streams. The mixedmode preamble includes a signal field corresponding to information aboutthe data packet. The signal field includes a first sub-field thatindicates a number of streams of the second portion of the mixed modepreamble and a second sub-field indicating, based on the firstsub-field, whether to perform a beam change between the first portionand the second portion of the mixed mode preamble or whether to performchannel smoothing on the second portion of the mixed mode preamble. Themethod further includes transmitting, from the first wirelesscommunication device to a second wireless communication device, the datapacket having the mixed mode preamble.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an example wireless local area network including one or moredevices configured to implement mixed mode preamble beam change andsmoothing according to an embodiment of the present disclosure.

FIG. 2 is an example mixed mode preamble according to an embodiment ofthe present disclosure.

FIG. 3 is another example mixed mode preamble according to an embodimentof the present disclosure.

FIG. 4 is another example mixed mode preamble according to an embodimentof the present disclosure.

FIG. 5 is an example mixed mode preamble beam change and smoothingmethod performed by a transmitting device according to an embodiment ofthe present disclosure.

FIG. 6 is an example mixed mode preamble beam change and smoothingmethod performed by a receiving device according to an embodiment of thepresent disclosure.

In the drawings, reference numbers may be reused to identify similarand/or identical elements.

DESCRIPTION

Various IEEE 802.11 standards, such as IEEE 802.11n, 802.11ac, and802.11ah implement a mixed mode preamble (e.g., referred to as a “longpreamble” in IEEE 802.11ah). The mixed mode preamble includes a firstportion (referred to herein also as “omni portion”) that is to betransmitted omnidirectionally using a single stream and a second portion(also referred to herein as “beamformed portion”) that is transmitted ina beamformed manner using multiple streams. Specifically, mixed modepreambles include an omni portion to support multi-user multiple-inputmultiple-output (MU-MIMO) operation. For example only, the omni portionincludes a short training field (STF), a first long training field (LTFor LTF1), and a physical layer (PHY) signal field (SIG or SIG-A). TheSIG-A field includes information about (e.g., how to process) thebeamformed portion corresponding to the mixed mode preamble, and may bemodulated according to a binary phase-shift keying (BPSK) modulationscheme and/or a quadrature phase-shift keying (QPSK) modulation scheme.The beamformed portion of the mixed mode preamble follows the SIG field.Some omni portions (e.g., IEEE 802.11ac omni portions) include a legacysignal field (e.g., between LTF and SIG-A). The LTF may include doubleguard interval (DGI) and one or more long training sequences (LTS).

The SIG field in the omni portion of the mixed mode preamble (SIG-A)includes an N_(STS) indication. N_(STS) indicates a number of streams(e.g., corresponding to a number of transmit antennas) of the beamformedportion being transmitted from the device. For example, if N_(STS)=1,only a single stream is being transmitted. Conversely, if N_(STS)>1,multiple (N_(TX)) transmit antennas will transmit the beamformedportion.

Regardless whether N_(STS)>1 (i.e., whether multiple transmit antennaswill be used to transmit the beamformed portion), the omni portion isstill transmitted via a single spatial stream (e.g., the omni portionmay be modulated similar to legacy wireless local area network (WLAN)standards such as 802.11a, 802.11g, etc.), and is mapped to N_(TX)transmit antennas by a spatial mapping matrix Q_(k) ^((omni)) for a k-thtone according to x_(k)=Q_(k) ^((omni))s_(k), where x_(k) corresponds tothe transmitted vector in tone k, of size N_(TX)×1, Q_(k) ^((omni))corresponds to the spatial mapping matrix for the omni portion in tonek, of size N_(TX)×1, and s_(k) corresponds to an original single streamsignal in tone k, of size 1×1.

Conversely, the beamformed portion may be modulated with N_(STS)space-time streams (i.e., MIMO) and mapped to NTX transmit antennas byspatial mapping matrix Q_(k) ^((data)) for the k-th tone according tox_(k)=Q_(k) ^((data))D_(CSD.k)s_(k), where x_(k) corresponds to thetransmitted vector in tone k, of size N_(TX)×1, Q_(k) ^((data))corresponds to the spatial mapping matrix for the beamformed portion intone k, of size N_(TX)×N_(STS), D_(CSD.k) corresponds to the diagonalmatrix with diagonal values representing per-stream cyclic shiftdiversity (CSD) phase shiftings in tone k, of size N_(STS)×N_(STS) ands_(k) corresponds an original single or multi-stream signal in tone k,of size N_(STS)×1.

Systems and methods according to the principles of the presentdisclosure provide an additional bit (in embodiments, one or more bits)in the SIG-A field of the omni portion. For example, this additional bitmay be referred to as a “beam-change/smoothing” (bc/s) bit. Forreference, the terms “smoothing” and “beamforming” correspond to usagein, for example, standards 802.11n, 802.11ac, etc. The term “beamchange” corresponds to a beam change indication.

In one embodiment, a receiving device (i.e., a device that receives thesignal including the omni portion of the mixed mode preamble) interpretsthe bc/s bit differently according to other values in the SIG-A field.For example, in such an embodiment, the receiving device interprets thebc/s bit differently based on the value of N_(STS). In other words, thevalue of the bc/s bit (e.g., a 1 or a 0) may provide more than oneindication to the receiver in different circumstances. For example, a 1or 0 in the bc/s bit field may correspond to a recommendation, to thereceiver, of whether to perform a beam change (1) or not (0) ifN_(STS)=1. Conversely, a 1 or 0 in the bc/s bit field may recommend, tothe receiver, whether to perform smoothing (1) or not (0) if N_(STS)>1.In other words, the number of space-time streams (N_(STS)) to be used tocarry the beamformed portion of the same packet controls theinterpretation of the bc/s bit. Accordingly, the bc/s bit may bothindicate a change between use of the Q_(k) ^((omni)) and Q_(k) ^((data))matrices, as well as the smoothability of the beamformed portion channelestimation (e.g., based on data long training fields, or D-LTF (1 . . .N), in the beamformed portion).

FIG. 1 shows an example WLAN 100 including one or more wirelesscommunication devices configured to implement the mixed mode preamblebeam change and smoothing systems and methods according to an embodimentof the present disclosure. The WLAN 100 includes an access point (AP)104 having a host processor 108 in communication with a networkinterface 112. The network interface 112 includes a medium accesscontrol (MAC) device 116 and a physical layer (PHY) device 120. The PHYdevice 120 includes a plurality of transceivers 124-1, 124-2, . . . ,and 124-n, referred to collectively as transceivers 124. Thetransceivers 124 communicate with respective antennas 128-1, 128-2, . .. , and 128-n, referred to collectively as antennas 128.

The AP 104 communicates with a plurality of client stations 132-1,132-2, 132-3, . . . , and 132-n, referred to collectively as clientstations 132. The client station 132-1 includes a host processor 136 incommunication with a network interface 140. The network interface 140includes a MAC device 144 and a PHY device 148. The PHY device 148includes a plurality of transceivers 152-1, 152-2, . . . , and 152-n,referred to collectively as transceivers 152. The transceivers 152communicate with respective antennas 156-1, 156-2, . . . , and 156-n,referred to collectively as antennas 128. One or more of the clientstations 132 may have a same or similar structure as the client station132-1. For example only, each of the client stations 132 may have a sameor different number of the transceivers 152 and the antennas 156.

The host processor 108, the MAC device 144, and/or the PHY device 120 ofthe AP 104 may be configured to generate data packets including themixed mode preamble according to the principles of the presentdisclosure. Accordingly, the mixed mode preamble includes an omniportion and a beamformed portion. For example, the SIG-A field of theomni portion includes an additional beam-change/smoothing (bc/s) bit.The bc/s bit indicates whether beam change or smoothing is recommendedbased on a value of N_(STS). The transceivers 124 are configured totransmit the data packets via the respective antennas 128.

Conversely, respective receiving devices (i.e., the client stations 132)are configured to selectively process the data packets received from theAP 104, via antennas 156, according to the bc/s bit in the mixed modepreamble.

For example, Q_(k) ^((omni)) may be equal to Q_(k) ^((data)) (i.e., thespatial mapping between the omni portion and the beamformed portion maybe the same) when the beamformed portion is modulated as a singlespace-time stream (i.e., when N_(STS)=1). In other words, because theomni portion is always modulated as a single space time stream, Q_(k)^((omni)) may be equal to Q_(k) ^((data)) when the beamformed portion ismodulated, like the omni portion, as a single space-time stream.However, when N_(STS)=1, the spatial mapping between the omni portionand the beamformed portion may be the same or different. For example,the spatial mapping between the omni portion and the beamformed portionmay be different if beamforming is performed. Accordingly, if N_(STS)=1,then the bc/s bit is set (e.g., to 1) to instruct the receiving deviceto perform a beam change if the spatial mapping between the omni portionand the beamformed portion is different. Conversely, if N_(STS)=1 andthe spatial mapping between the omni portion and the beamformed portionis the same, then the bc/s is not set (e.g., set to 0).

Accordingly, when N_(STS)=1, the bc/s bit indicates to the receivingdevice when to transition between the spatial mapping of the omniportion, Q_(k) ^((omni)), and the spatial mapping of the beamformedportion, Q_(k) ^((data)). Setting the bc/s bit to 1 indicates that Q_(k)^((omni)) is not equal to Q_(k) ^((data)) for at least one of theoverlapping non-zero tones between the omni portion and the beamformedportion, and therefore the receiving device should perform a beamchange. Further, the bc/s bit being set to 1 may also indicate arecommendation for the receiving device not to conduct channel smoothingacross adjacent tones for the beamformed portion channel estimations.For example, when bc/s=1, the transmitting device may be performingtransmit beamforming (TxBF) on the beamformed portion, and performingsmoothing in this situation may degrade performance.

Conversely, not setting the bc/s bit (i.e., setting the bc/s bit to 0)when N_(STS)=1 indicates a recommendation for the receiving device notto perform a beam change between the omni portion and the beamformedportion. In some implementations (e.g., for an 802.11ah long preamble),when the beam is not changed, the receiving device may combine channelestimations of LTF1 of the omni portion and D-LTF1 of the beamformedportion.

When N_(STS)>1, the bc/s bit indicates to the receiving device whetherchannel smoothing is recommended. For example, when N_(STS)>1 and thebc/s bit is set (i.e., set to 1), it is recommended for the receivingdevice to perform channel smoothing on the beamformed portion. WhenN_(STS)>1 and the bc/s bit is not set (i.e., set to 0), it isrecommended for the receiving device to not perform channel smoothing onthe beamformed portion. In some implementations, when N_(STS)>1, thebc/s bit may be used to indicate whether to perform beamforming.

FIG. 2 shows an example mixed mode preamble 200 generated andtransmitted by a transmitting device (e.g., the AP 104 of FIG. 1) andreceived by a receiving device (e.g., one of the client stations 132 ofFIG. 1) according to an embodiment of the present disclosure. Thepreamble 200 includes an omni portion 204 and a beamformed portion 208.The omni portion 204 includes an STF 212, an LTF1 216, and a PHY SIG-A220. The beamformed portion 208 includes a beamformed portion shorttraining field (D-STF) 224, D-LTF1 . . . DTFN 228, a PHY SIG-B 232, anddata 236.

The SIG-A field 220 includes a plurality of sub-fields 240 (S-F₁ . . .S-F_(n)). The sub-fields 240 include an N_(STS) field and a bc/s field(bit). The transmitting device selectively sets the bc/s bit asdescribed above according to an embodiment of the present disclosure.The receiving device interprets the bc/s bit based on the value of theN_(STS) field.

FIG. 3 shows another example mixed mode preamble 300 generated andtransmitted by a transmitting device (e.g., the AP 104 of FIG. 1) andreceived by a receiving device (e.g., one of the client stations 132 ofFIG. 1) according to an embodiment of the present disclosure. Instead ofa single bc/s bit, the SIG-A field 220 of the preamble 300 includes abeam change (bc) bit and a smoothing (or, in some implementations,beamforming) bit s. In other words, instead of using a singlebeam-change/smoothing bit, the SIG-A field 220 includes separate bc ands bits. Accordingly, regardless of whether N_(STS) is greater than 1,the bc bit indicates whether to perform a beam change. For example, whenN_(STS)>1, the bc bit is set to 1. Conversely, the s bit indicateswhether to perform smoothing (or, in some implementations whether toperform beamforming).

FIG. 4 shows another example mixed mode preamble 400 generated andtransmitted by a transmitting device (e.g., the AP 104 of FIG. 1) andreceived by a receiving device (e.g., one of the client stations 132 ofFIG. 1) according to an embodiment of the present disclosure. The SIG-Afield 220 of the preamble 400 includes a beam change bit bc.Accordingly, bc indicates whether to perform a beam change regardless ofwhether N_(STS) is greater than 1. If N_(STS) is greater than 1, thanthe value of bc will also be 1 to indicate that a beam change should beperformed.

In some implementations, the mixed mode preamble may include only theadditional bc bit as shown in FIG. 4, which is set to indicate that abeam change should be performed by the receiving device, and not set toindicate that a beam change should not be performed by the receivingdevice. However, the interpretation of the bc bit by the receivingdevice may vary depending on whether N_(STS) is 1 or greater than 1.

For example, if N_(STS) is 1, indicating a single space-time stream, andbc is set to 1, then Q_(k) ^((omni)) is not equal to Q_(k) ^((data)) forat least one of the overlapping non-zero tones between the omni portionand the beamformed portion. Accordingly, bc being set to 1 alsoindicates a recommendation that the receiving device should not performchannel smoothing across adjacent tones for the beamformed portionchannel estimations due to the likelihood that the transmitting deviceis performing transmission beam forming TxBF on the beamformed portion.Conversely, if N_(STS) is 1 and bc is set to 0, then Q_(k) ^((omni)) isequal to Q_(k) ^((data)) in all of the overlapping non-zero tonesbetween the omni portion and the beamformed portion.

If N_(STS) is greater than one, indicating more than one space-timestream, and bc is set to 1, Q_(k) ^((omni)) is different from thecorresponding spatial mapping matrix for D-LTF1. In other words, Q_(k)^((omni)) is not equal to Q_(k) ^((data))D_(k) ^((CSD))P₁ for at leastone of the overlapping non-zero tones between the omni portion and thebeamformed portion, where P₁ corresponds to a first column of aspreading P matrix. Accordingly, LTF1 and D-LTF1 are spatially mappeddifferently (for example, as a result of beamforming or differentspatial mapping in the beamformed portion). Further, regardless ofwhether beamforming is being performed, it is recommended that channelsmoothing is not performed by the receiving device when bc is set to 1.In some implementations, an additional smoothing bit s may be used toindicate whether channel smoothing should be performed.

If N_(STS) is greater than one, indicating more than one space-timestream, and bc is not set (i.e., is set to 0), then Q_(k) ^((omni)) isequal to Q_(k) ^((data))D_(k) ^((CSD))P₁ for all of the overlappingnon-zero tones between the omni portion and the beamformed portion. Forexample, for multiple space-time streams, multi-streams in each datapacket are trained using the D-LTFs as spread by the P matrix accordingto [DLTF₁, DLTF₂, . . . DLTF_(N) _(LTF) ]=Q_(k) ^((data))D_(k)^(CSD)P_(LTF)LTF_(k), where Q_(k) ^((data)) corresponds to a spatialmapping matrix for multi-streams of size N_(TX)×N_(STS), D_(k) ^(CSD)corresponds to a diagonal matrix reflecting phase shifts on differentstreams caused by per-stream CSD, P_(LTF) corresponds to the spreading Pmatrix of size N_(STS)×N_(LTF), and LTF_(k) corresponds to an LTF sign(1 or −1) in tone k, of size 1×1. Accordingly, if N_(STS) is greaterthan one, indicating more than one space-time stream, and be is not set,then Q_(k) ^((omni)) is equal to Q_(k) ^((data))D_(k) ^((CSD))P₁. Inother words, the spatial mapping for LTF1 and the spatial mapping forD-LTF1 are the same, and the receiving device may combine LTF1 withD-LTF1 to improve channel estimations.

FIG. 5 shows an example mixed mode preamble beam change and smoothingmethod 500 as performed by a transmitting device according to anembodiment of the present disclosure. At 504, the method 500 determineswhether a number of space-time streams N_(STS) is greater than 1. Iffalse, the method 500 continues to 508. If true, the method 500continues to 512. At 508, the method 500 determines whether to indicatea recommendation, to a receiving device, to perform a beam changebetween an omni portion and a beamformed portion. If true, the method500 continues to 516. If false, the method 500 continues to 520. At 516,the method 500 sets a bc/s bit in the SIG-A field of a mixed modepreamble to 1. At 520, the method 500 sets the bc/s bit to 0. At 524,the transmitting device transmits the mixed mode preamble including anN_(STS) field indicating the number of space-time streams to be used fortransmitting the beamformed portion and the bc/s bit.

At 512, the method 500 determines whether to indicate a recommendation,to the receiving device, to perform channel smoothing on the beamformedportion. If true, the method 500 continues to 528. If false, the method500 continues to 532. At 528, the method 500 sets the bc/s bit to 1. At532, the method 500 sets the bc/s bit to 0. The method 500 thentransmits the mixed mode preamble at 524 and ends at 536.

FIG. 6 shows an example mixed mode preamble beam change and smoothingmethod 600 as performed by a receiving device according to an embodimentof the present disclosure. At 604, the method 600 receives a mixed modepreamble of a data packet. At 608, the method 600 determines, based onan N_(STS) sub field in a SIG-A field of an omni portion of the mixedmode preamble, a number of space-time streams N_(STS) being used totransmit a beamformed portion of the mixed mode preamble and determineswhether N_(STS) is greater than 1. If true, the method 600 continues to612. If false, the method 600 continues to 616.

At 612, the method 600 determines whether the bc/s bit in the SIG-Afield is set. If true, the method 600 continues to 620. If false, themethod 600 continues to 624. At 620, the method 600 performs channelsmoothing on the beamformed portion of the mixed mode preamble. At 624,the method 600 processes the beamformed portion of the mixed modepreamble without performing channel smoothing.

At 616, the method 600 determines whether the bc/s bit in the SIG-Afield is set. If true, the method 600 continues to 628. If false, themethod 600 continues to 632. At 628, the method 600 performs a beamchange between the omni portion and the beamformed portion. In someimplementations, the method 600 performs the beam change but does notperform channel smoothing. At 632, the method 600 processes thebeamformed portion of the mixed mode preamble without performing a beamchange. The method 600 ends at 636.

The wireless communications described in the present disclosure can beconducted in full or partial compliance with IEEE standard 802.11-2012,IEEE standard 802.16-2009, IEEE standard 802.20-2008, and/or BluetoothCore Specification v4.0. In various implementations, Bluetooth CoreSpecification v4.0 may be modified by one or more of Bluetooth CoreSpecification Addendums 2, 3, or 4. In various implementations, IEEE802.11-2012 may be supplemented by draft IEEE standard 802.11ac, draftIEEE standard 802.11ad, and/or draft IEEE standard 802.11ah.

Further aspects of the present disclosure relates to one or more of thefollowing clauses. A first wireless communication device includes aphysical layer device configured to generate a data packet having amixed mode preamble. The mixed mode preamble includes a first portion tobe transmitted omnidirectionally via a single stream, and a secondportion to be transmitted in a beamformed manner via a single stream ormultiple streams. The mixed mode preamble includes a signal fieldcorresponding to information about the data packet. The signal fieldincludes a first sub-field that indicates a number of streams of thesecond portion of the mixed mode preamble and a second sub-fieldindicating, based on the first sub-field, whether to perform a beamchange between the first portion and the second portion of the mixedmode preamble or whether to perform channel smoothing on the secondportion of the mixed mode preamble. A transceiver is configured totransmit, from the first wireless communication device to a secondwireless communication device, the data packet having the mixed modepreamble.

The second sub-field is a single bit. The first sub-field includes avalue N_(STS) indicating the number of streams of the second portion tobe transmitted. The second sub-field indicates whether to perform thebeam change between the first portion and the second portion of themixed mode preamble if the number of streams of the second portion to betransmitted is one. If the number of streams of the second portion to betransmitted is one, the second sub-field has a first value to indicate arecommendation, to the second wireless communication device, to performthe beam change between the first portion and the second portion of themixed mode preamble and a second value to indicate a recommendation, tothe second wireless communication device, not to perform the beam changebetween the first portion and the second portion of the mixed modepreamble.

The second sub-field indicates whether to perform the channel smoothingon the second portion of the mixed mode preamble if the number ofstreams of the second portion to be transmitted is greater than one. Ifthe number of streams of the second portion to be transmitted is greaterthan one, the second sub-field has a first value to indicate arecommendation, to the second wireless communication device, to performthe channel smoothing on the second portion of the mixed mode preambleand a second value to indicate a recommendation, to the second wirelesscommunication device, not to perform the channel smoothing on the secondportion of the mixed mode preamble.

A system includes the first wireless communication device of claim andthe second wireless communication device. The second wirelesscommunication device is configured to receive the mixed mode preamblefrom the first wireless communication device, determine, based on thefirst sub-field, a number of streams of the second portion of the mixedmode preamble to be transmitted by the first wireless communicationdevice, and determine, based on the number of streams of the secondportion of the mixed mode preamble that will be transmitted by the firstwireless communication device and the second sub-field, whether toperform the beam change between the first portion and the second portionor whether to perform the channel smoothing on the second portion. Thesecond wireless communication device is configured to determine whetherto perform the beam change on the second portion of the mixed modepreamble if the number of streams of the second portion to betransmitted is one. The second wireless communication device isconfigured to determine whether to perform the channel smoothing if thenumber of streams of the second portion to be transmitted is greaterthan one.

A method of operating a first wireless communication device includesgenerating a data packet having a mixed mode preamble. The mixed modepreamble includes a first portion to be transmitted omnidirectionallyvia a single stream, and a second portion to be transmitted in abeamformed manner via a single stream or multiple streams. The mixedmode preamble includes a signal field corresponding to information aboutthe data packet. The signal field includes a first sub-field thatindicates a number of streams of the second portion of the mixed modepreamble and a second sub-field indicating, based on the firstsub-field, whether to perform a beam change between the first portionand the second portion of the mixed mode preamble or whether to performchannel smoothing on the second portion of the mixed mode preamble. Themethod further includes transmitting, from the first wirelesscommunication device to a second wireless communication device, the datapacket having the mixed mode preamble.

The second sub-field is a single bit. The first sub-field includes avalue N_(STS) indicating the number of streams of the second portion tobe transmitted. The second sub-field indicates whether to perform thebeam change between the first portion and the second portion of themixed mode preamble if the number of streams of the second portion to betransmitted is one. If the number of streams of the second portion to betransmitted is one, the second sub-field has a first value to indicate arecommendation, to the second wireless communication device, to performthe beam change between the first portion and the second portion of themixed mode preamble and a second value to indicate a recommendation, tothe second wireless communication device, not to perform the beam changebetween the first portion and the second portion of the mixed modepreamble.

The second sub-field indicates whether to perform the channel smoothingon the second portion of the mixed mode preamble if the number ofstreams of the second portion to be transmitted is greater than one. Ifthe number of streams of the second portion to be transmitted is greaterthan one, the second sub-field has a first value to indicate arecommendation, to the second wireless communication device, to performthe channel smoothing on the second portion of the mixed mode preambleand a second value to indicate a recommendation, to the second wirelesscommunication device, not to perform the channel smoothing on the secondportion of the mixed mode preamble.

The method further includes, using the second wireless communicationdevice, receiving the mixed mode preamble from the first wirelesscommunication device, determining, based on the first sub-field, anumber of streams of the second portion of the mixed mode preamble to betransmitted by the first wireless communication device, and determining,based on the number of streams of the second portion of the mixed modepreamble that will be transmitted by the first wireless communicationdevice and the second sub-field, whether to perform the beam changebetween the first portion and the second portion or whether to performthe channel smoothing on the second portion. The method furtherincludes, using the second wireless communication device, determiningwhether to perform the beam change on the second portion of the mixedmode preamble if the number of streams of the second portion to betransmitted is one. The method further includes, using the secondwireless communication device, determining whether to perform thechannel smoothing if the number of streams of the second portion to betransmitted is greater than one.

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims. As used herein, the phrase atleast one of A, B, and C should be construed to mean a logical (A OR BOR C), using a non-exclusive logical OR, and should not be construed tomean “at least one of A, at least one of B, and at least one of C.” Itshould be understood that one or more steps within a method may beexecuted in different order (or concurrently) without altering anembodiment of the present disclosure.

In this application, including the definitions below, the term modulemay be replaced with the term circuit. The term module may refer to, bepart of, or include an Application Specific Integrated Circuit (ASIC); adigital, analog, or mixed analog/digital discrete circuit; a digital,analog, or mixed analog/digital integrated circuit; a combinationallogic circuit; a field programmable gate array (FPGA); a processor(shared, dedicated, or group) that executes code; memory (shared,dedicated, or group) that stores code executed by a processor; othersuitable hardware components that provide the described functionality;or a combination of some or all of the above, such as in asystem-on-chip.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes,and/or objects. The term shared processor encompasses a single processorthat executes some or all code from multiple modules. The term groupprocessor encompasses a processor that, in combination with additionalprocessors, executes some or all code from one or more modules. The termshared memory encompasses a single memory that stores some or all codefrom multiple modules. The term group memory encompasses a memory that,in combination with additional memories, stores some or all code fromone or more modules. The term memory is a subset of the termcomputer-readable medium. The term computer-readable medium, as usedherein, does not encompass transitory electrical or electromagneticsignals propagating through a medium (such as on a carrier wave); theterm computer-readable medium may therefore be considered tangible andnon-transitory. Non-limiting examples of a non-transitory, tangiblecomputer-readable medium include nonvolatile memory (such as flashmemory), volatile memory (such as static random access memory anddynamic random access memory), magnetic storage (such as magnetic tapeor hard disk drive), and optical storage.

The apparatuses and methods described in this application may bepartially or fully implemented by one or more computer programs executedby one or more processors. The computer programs includeprocessor-executable instructions that are stored on at least onenon-transitory, tangible computer-readable medium. The computer programsmay also include and/or rely on stored data.

What is claimed is:
 1. A first wireless communication device, comprising: a physical layer device configured to generate a data packet having a mixed mode preamble, wherein the mixed mode preamble includes (i) a first portion to be transmitted omnidirectionally via a single stream, and (ii) a second portion to be transmitted in a beamformed manner via a single stream or multiple streams, the mixed mode preamble includes a signal field corresponding to information about the data packet, and the signal field includes (i) a first sub-field that indicates a number of streams of the second portion of the mixed mode preamble and (ii) a second sub-field configured to selectively indicate, based on the first sub-field, (a) whether to perform a beam change between the first portion and the second portion of the mixed mode preamble and (b) whether to perform channel smoothing on the second portion of the mixed mode preamble, wherein the first-sub field controls which of (a) and (b) is indicated by the second sub-field, such that the second sub-field indicates whether to perform the beam change when the first sub-field corresponds to a first number of streams, and the second sub-field indicates whether to perform the channel smoothing when the first sub-field corresponds to a second number of streams; and a transceiver configured to transmit, from the first wireless communication device to a second wireless communication device, the data packet having the mixed mode preamble.
 2. The first wireless communication device of claim 1, wherein the first sub-field includes a value N_(STS) indicating the number of streams of the second portion to be transmitted.
 3. The first wireless communication device of claim 1, wherein the second sub-field indicates whether to perform the beam change between the first portion and the second portion of the mixed mode preamble if the number of streams of the second portion to be transmitted is one.
 4. The first wireless communication device of claim 3, wherein, if the number of streams of the second portion to be transmitted is one, the second sub-field has (i) a first value to indicate a recommendation, to the second wireless communication device, to perform the beam change between the first portion and the second portion of the mixed mode preamble and (ii) a second value to indicate a recommendation, to the second wireless communication device, not to perform the beam change between the first portion and the second portion of the mixed mode preamble.
 5. The first wireless communication device of claim 1, wherein the second sub-field indicates whether to perform the channel smoothing on the second portion of the mixed mode preamble if the number of streams of the second portion to be transmitted is greater than one.
 6. The first wireless communication device of claim 5, wherein, if the number of streams of the second portion to be transmitted is greater than one, the second sub-field has (i) a first value to indicate a recommendation, to the second wireless communication device, to perform the channel smoothing on the second portion of the mixed mode preamble and (ii) a second value to indicate a recommendation, to the second wireless communication device, not to perform the channel smoothing on the second portion of the mixed mode preamble.
 7. A system, comprising: the first wireless communication device of claim 1; and the second wireless communication device, wherein the second wireless communication device is configured to receive the mixed mode preamble from the first wireless communication device, determine, based on the first sub-field, a number of streams of the second portion of the mixed mode preamble to be transmitted by the first wireless communication device, and determine, based on (i) the number of streams of the second portion of the mixed mode preamble that will be transmitted by the first wireless communication device and (ii) the second sub-field, whether to (a) perform the beam change between the first portion and the second portion or (b) whether to perform the channel smoothing on the second portion.
 8. The system of claim 7, wherein the second wireless communication device is configured to determine whether to perform the beam change on the second portion of the mixed mode preamble if the number of streams of the second portion to be transmitted is one.
 9. The system of claim 7, wherein the second wireless communication device is configured to determine whether to perform the channel smoothing if the number of streams of the second portion to be transmitted is greater than one.
 10. The first wireless communication device of claim 1, wherein the second sub-field is a single bit.
 11. A method of operating a first wireless communication device, the method comprising: generating a data packet having a mixed mode preamble, wherein the mixed mode preamble includes (i) a first portion to be transmitted omnidirectionally via a single stream, and (ii) a second portion to be transmitted in a beamformed manner via a single stream or multiple streams, the mixed mode preamble includes a signal field corresponding to information about the data packet, and the signal field includes (i) a first sub-field that indicates a number of streams of the second portion of the mixed mode preamble and (ii) a second sub-field configured to selectively indicate, based on the first sub-field, (a) whether to perform a beam change between the first portion and the second portion of the mixed mode preamble and (b) whether to perform channel smoothing on the second portion of the mixed mode preamble, wherein the first-sub field controls which of (a) and (b) is indicated by the second sub-field, such that the second sub-field indicates whether to perform the beam change when the first sub-field corresponds to a first number of streams, and the second sub-field indicates whether to perform the channel smoothing when the first sub-field corresponds to a second number of streams; and transmitting, from the first wireless communication device to a second wireless communication device, the data packet having the mixed mode preamble.
 12. The method of claim 11, wherein the first sub-field includes a value N_(STS) indicating the number of streams of the second portion to be transmitted.
 13. The method of claim 11, wherein the second sub-field indicates whether to perform the beam change between the first portion and the second portion of the mixed mode preamble if the number of streams of the second portion to be transmitted is one.
 14. The method of claim 13, wherein, if the number of streams of the second portion to be transmitted is one, the second sub-field has (i) a first value to indicate a recommendation, to the second wireless communication device, to perform the beam change between the first portion and the second portion of the mixed mode preamble and (ii) a second value to indicate a recommendation, to the second wireless communication device, not to perform the beam change between the first portion and the second portion of the mixed mode preamble.
 15. The method of claim 11, wherein the second sub-field indicates whether to perform the channel smoothing on the second portion of the mixed mode preamble if the number of streams of the second portion to be transmitted is greater than one.
 16. The method of claim 15, wherein, if the number of streams of the second portion to be transmitted is greater than one, the second sub-field has (i) a first value to indicate a recommendation, to the second wireless communication device, to perform the channel smoothing on the second portion of the mixed mode preamble and (ii) a second value to indicate a recommendation, to the second wireless communication device, not to perform the channel smoothing on the second portion of the mixed mode preamble.
 17. The method of claim 11, further comprising: using the second wireless communication device, receiving the mixed mode preamble from the first wireless communication device, determining, based on the first sub-field, a number of streams of the second portion of the mixed mode preamble to be transmitted by the first wireless communication device, and determining, based on (i) the number of streams of the second portion of the mixed mode preamble that will be transmitted by the first wireless communication device and (ii) the second sub-field, whether to (a) perform the beam change between the first portion and the second portion or (b) whether to perform the channel smoothing on the second portion.
 18. The method of claim 17, further comprising, using the second wireless communication device, determining whether to perform the beam change on the second portion of the mixed mode preamble if the number of streams of the second portion to be transmitted is one.
 19. The method of claim 17, further comprising, using the second wireless communication device, determining whether to perform the channel smoothing if the number of streams of the second portion to be transmitted is greater than one.
 20. The method of claim 11, wherein the second sub-field is a single bit. 